Average session length
Engagement metric. How often and how deeply do they use it?
What is average session length?
Average session length is the mean time a user spends in an app per session, from opening it to leaving or timing out.
Session: one continuous period of use, ended by closing the app or by a period of inactivity.
How to calculate Session length
Average session length = Total session time ÷ Number of sessions- Total session time
- the summed foreground time of all sessions in the period
- Number of sessions
- the count of separate sessions
Where definitions differ
| Variant | Formula | When to use it |
|---|---|---|
| Mean session length | Total time ÷ Sessions | Pulled up by a few very long sessions. |
| Median session length | Middle session duration | Closer to a typical session. |
| Timeout rule | A session ends after a set period of inactivity | 30 minutes is a common default, including in Google Analytics 4; a shorter timeout splits sessions and lowers the average. |
Session length calculator
Example inputs: change them to your own numbers. The examples only make the calculator show a worked answer; they are not benchmarks or targets. Runs in your browser; nothing you type is sent anywhere.
- Average session length
- 5 min
Is a longer session always better?
No. For utility apps, such as payments, a short session can mean the task was easy. Session length is a good sign only when longer sessions mean more of the value the app is for.
How Session length differs by vertical
| EdTech | Compare with lesson length; sessions much shorter than a lesson mean lessons go unfinished. |
|---|---|
| Fintech | Short is often good; long sessions on a payment screen can signal confusion. |
| OTT and streaming | Tied closely to watch time. |
| Gaming | Used with sessions per day to judge engagement depth. |
Common mistakes
- Comparing session length across tools with different timeouts.
- Treating a rising session length as success in a task-based app.
Questions
How do you calculate average session length?
Divide total session time by the number of sessions. 120k minutes across 24k sessions is an average of 5 minutes.
Why does session length differ between analytics tools?
Tools end sessions with different inactivity timeouts and some drop very short sessions. Those rules change both the number of sessions and their length.
Should I report mean or median session length?
Both if you can. The mean is what most dashboards show; the median is closer to a typical session when a few users stay in the app for hours.
Which currency do the calculators use?
The calculators show US dollars, but every formula works in any currency: enter your own figures in the currency you report in and read the results in that currency.
What is the difference between a metric and a KPI?
A metric is any measured quantity; a KPI is a metric a team has chosen as a target for judging performance. Most metrics here become KPIs only for the teams whose work moves them.
Do I need an MMP to measure these metrics?
Not for all of them. Engagement and monetisation metrics come from product analytics and billing data, while metrics split by ad channel, such as CPI, ROAS or retention by source, need installs attributed to campaigns.